A metering and mixing device is known, for example, from the document DE 32 33 366 A1, for mixing a dental impression material made of two pasty components. The device described therein for mixing the components of a dental impression material includes a mixer designed as a disposable part and having a base body. The mixer includes a mixing chamber, several feed channels for components of impression material which open separately from each other into the mixing chamber, as well as an outlet opening for the mixed impression material. The mixer includes a mixer part which is rotatably arranged in the mixing chamber and driven by a driving device to which the mixer is secured detachably. The components of the impression material are contained in reservoir cylinders and they are pushed by pistons into the mixing chamber, and pushed out after the mixing via the outlet opening into the impression spoon. By way of a control unit, the rate of advance can be varied by the setting actuators of the pistons, so that both the ratio of the piston advance rate which determines the curing time of the impression material and also the total advance or the duration of the advance, and thus the impression material quantity, can be controlled.
Such metering and mixing devices can have issues with metering accuracy, for example, at high quantitative ratios of the individual components, such as 50:1 or higher, for example.
U.S. Pat. No. 6,176,396 B1 describes a metering and mixing device for multi-component substances, in particular multi-component adhesives, with a single cartridge accommodating device, for accommodating replaceable cartridges having individual substance components, a discharging device for simultaneously discharging the substance components from the cartridges through the component outlets by way of discharging pistons that plunge into the cartridge accommodation device or cartridges, and a mixing device connected to the component outlets which mixes the discharge substance components and outputs them in the mixed state. For driving the discharging pistons, a threaded bar is used in each case, which is introduced into a thread located in a central position in the discharging piston, and which moves the discharging piston forward by the simultaneous rotation of the threaded bars relative to the respective discharging piston. With this metering and mixing device, the threaded bars have to already be plunged with their full length into the individual components to be mixed, and thus, for example, simple tubular cartridges can no longer be used in a simple manner; instead special cartridges are involved which must already have, within their central inner space, the space needed for the threaded bars extending through the cartridges.